Abstract : The usefullness of utilizing electron microscopy in wear studies is illustrated by observations of the surface topography and subsurface microstructure of nickel-on-nickel specimens tested in dynamic wear in a nitrogen atmosphere. The nickel surfaces have a smeared and layered appearance. The subsurface microstructure has been observed as a function of depth below the wear surface; the structure is quite varied. Regions of extremely high dislocation density, characteristic of a high degree of plastic deformation, are seen, and regions of extremely fine grains (less than 0.0001 cm) are observed, showing that locally recrystallization has occurred due to a rather high temperature being attained. The substructure alterations extend down to 0.01 cm below the surface. It is clear that electron microscopic observations are indispensable in any detailed wear study. (Author)